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      1 #ifndef _LINUX_FUTEX_H
      2 #define _LINUX_FUTEX_H
      3 
      4 #include <linux/sched.h>
      5 
      6 /* Second argument to futex syscall */
      7 
      8 
      9 #define FUTEX_WAIT		0
     10 #define FUTEX_WAKE		1
     11 #define FUTEX_FD		2
     12 #define FUTEX_REQUEUE		3
     13 #define FUTEX_CMP_REQUEUE	4
     14 #define FUTEX_WAKE_OP		5
     15 #define FUTEX_LOCK_PI		6
     16 #define FUTEX_UNLOCK_PI		7
     17 #define FUTEX_TRYLOCK_PI	8
     18 
     19 /*
     20  * Support for robust futexes: the kernel cleans up held futexes at
     21  * thread exit time.
     22  */
     23 
     24 /*
     25  * Per-lock list entry - embedded in user-space locks, somewhere close
     26  * to the futex field. (Note: user-space uses a double-linked list to
     27  * achieve O(1) list add and remove, but the kernel only needs to know
     28  * about the forward link)
     29  *
     30  * NOTE: this structure is part of the syscall ABI, and must not be
     31  * changed.
     32  */
     33 struct robust_list {
     34 	struct robust_list __user *next;
     35 };
     36 
     37 /*
     38  * Per-thread list head:
     39  *
     40  * NOTE: this structure is part of the syscall ABI, and must only be
     41  * changed if the change is first communicated with the glibc folks.
     42  * (When an incompatible change is done, we'll increase the structure
     43  *  size, which glibc will detect)
     44  */
     45 struct robust_list_head {
     46 	/*
     47 	 * The head of the list. Points back to itself if empty:
     48 	 */
     49 	struct robust_list list;
     50 
     51 	/*
     52 	 * This relative offset is set by user-space, it gives the kernel
     53 	 * the relative position of the futex field to examine. This way
     54 	 * we keep userspace flexible, to freely shape its data-structure,
     55 	 * without hardcoding any particular offset into the kernel:
     56 	 */
     57 	long futex_offset;
     58 
     59 	/*
     60 	 * The death of the thread may race with userspace setting
     61 	 * up a lock's links. So to handle this race, userspace first
     62 	 * sets this field to the address of the to-be-taken lock,
     63 	 * then does the lock acquire, and then adds itself to the
     64 	 * list, and then clears this field. Hence the kernel will
     65 	 * always have full knowledge of all locks that the thread
     66 	 * _might_ have taken. We check the owner TID in any case,
     67 	 * so only truly owned locks will be handled.
     68 	 */
     69 	struct robust_list __user *list_op_pending;
     70 };
     71 
     72 /*
     73  * Are there any waiters for this robust futex:
     74  */
     75 #define FUTEX_WAITERS		0x80000000
     76 
     77 /*
     78  * The kernel signals via this bit that a thread holding a futex
     79  * has exited without unlocking the futex. The kernel also does
     80  * a FUTEX_WAKE on such futexes, after setting the bit, to wake
     81  * up any possible waiters:
     82  */
     83 #define FUTEX_OWNER_DIED	0x40000000
     84 
     85 /*
     86  * The rest of the robust-futex field is for the TID:
     87  */
     88 #define FUTEX_TID_MASK		0x3fffffff
     89 
     90 /*
     91  * This limit protects against a deliberately circular list.
     92  * (Not worth introducing an rlimit for it)
     93  */
     94 #define ROBUST_LIST_LIMIT	2048
     95 
     96 long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout,
     97 	      u32 __user *uaddr2, u32 val2, u32 val3);
     98 
     99 extern int
    100 handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
    101 
    102 #ifdef CONFIG_FUTEX
    103 extern void exit_robust_list(struct task_struct *curr);
    104 extern void exit_pi_state_list(struct task_struct *curr);
    105 #else
    106 static inline void exit_robust_list(struct task_struct *curr)
    107 {
    108 }
    109 static inline void exit_pi_state_list(struct task_struct *curr)
    110 {
    111 }
    112 #endif
    113 
    114 #define FUTEX_OP_SET		0	/* *(int *)UADDR2 = OPARG; */
    115 #define FUTEX_OP_ADD		1	/* *(int *)UADDR2 += OPARG; */
    116 #define FUTEX_OP_OR		2	/* *(int *)UADDR2 |= OPARG; */
    117 #define FUTEX_OP_ANDN		3	/* *(int *)UADDR2 &= ~OPARG; */
    118 #define FUTEX_OP_XOR		4	/* *(int *)UADDR2 ^= OPARG; */
    119 
    120 #define FUTEX_OP_OPARG_SHIFT	8	/* Use (1 << OPARG) instead of OPARG.  */
    121 
    122 #define FUTEX_OP_CMP_EQ		0	/* if (oldval == CMPARG) wake */
    123 #define FUTEX_OP_CMP_NE		1	/* if (oldval != CMPARG) wake */
    124 #define FUTEX_OP_CMP_LT		2	/* if (oldval < CMPARG) wake */
    125 #define FUTEX_OP_CMP_LE		3	/* if (oldval <= CMPARG) wake */
    126 #define FUTEX_OP_CMP_GT		4	/* if (oldval > CMPARG) wake */
    127 #define FUTEX_OP_CMP_GE		5	/* if (oldval >= CMPARG) wake */
    128 
    129 /* FUTEX_WAKE_OP will perform atomically
    130    int oldval = *(int *)UADDR2;
    131    *(int *)UADDR2 = oldval OP OPARG;
    132    if (oldval CMP CMPARG)
    133      wake UADDR2;  */
    134 
    135 #define FUTEX_OP(op, oparg, cmp, cmparg) \
    136   (((op & 0xf) << 28) | ((cmp & 0xf) << 24)		\
    137    | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
    138 
    139 #endif
    140